You should still be able to get the staff through making it through Illusen's quests. So I can't foresee it being not obtainable in the future due to that. Right now there will likely be a large influx of staff into the amrket that can drop the price then eventually once the even is over there will be the slow trickly of them again into the market trough Illusen Quests.
The paintbrushes may be a decent investment to hoard since you can no longer get them from the HT. However you would have to hold on for a while since there are so many of them that will be obtained through the event.